amcheck/verify_heapam doesn't check for interrupts
I just noticed that the new heapam amcheck verification code can take
a very long time to respond to cancellations from pg_amcheck -- I saw
that it took over 2 minutes on a large database on my workstation.
It looks like we neglect to call CHECK_FOR_INTERRUPTS() anywhere
inside verify_heapam.c. Is there any reason for this? Can't we just
put a CHECK_FOR_INTERRUPTS() at the top of the outermost loop, inside
verify_heapam()?
Not sure if pg_amcheck itself is a factor here too -- didn't get that far.
Thanks
--
Peter Geoghegan
On Aug 26, 2021, at 2:38 PM, Peter Geoghegan <pg@bowt.ie> wrote:
It looks like we neglect to call CHECK_FOR_INTERRUPTS() anywhere
inside verify_heapam.c. Is there any reason for this?
Not any good one that I can see.
Can't we just
put a CHECK_FOR_INTERRUPTS() at the top of the outermost loop, inside
verify_heapam()?
I expect we could.
Not sure if pg_amcheck itself is a factor here too -- didn't get that far.
That runs an event loop in the client over multiple checks (heap and/or btree) running in backends, just as reindexdb and vacuumdb do over parallel reindexes and vacuums running in backends. It should be just as safe to ctrl-c out of pg_amcheck as out of those two. They all three use fe_utils/cancel.h's setup_cancel_handler(), so I would expect modifying verify_heapam would be enough.
—
Mark Dilger
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
On Thu, Aug 26, 2021 at 4:24 PM Mark Dilger
<mark.dilger@enterprisedb.com> wrote:
On Aug 26, 2021, at 2:38 PM, Peter Geoghegan <pg@bowt.ie> wrote:
It looks like we neglect to call CHECK_FOR_INTERRUPTS() anywhere
inside verify_heapam.c. Is there any reason for this?Not any good one that I can see.
Seems that way. Want to post a patch?
Not sure if pg_amcheck itself is a factor here too -- didn't get that far.
That runs an event loop in the client over multiple checks (heap and/or btree) running in backends, just as reindexdb and vacuumdb do over parallel reindexes and vacuums running in backends. It should be just as safe to ctrl-c out of pg_amcheck as out of those two. They all three use fe_utils/cancel.h's setup_cancel_handler(), so I would expect modifying verify_heapam would be enough.
Right. I checked that out myself, after sending my email from earlier.
We don't have any problems when pg_amcheck happens to be verifying a
B-Tree index -- verify_nbtree.c already has CHECK_FOR_INTERRUPTS() at
a few key points.
--
Peter Geoghegan
On Aug 26, 2021, at 4:39 PM, Peter Geoghegan <pg@bowt.ie> wrote:
Not any good one that I can see.
Seems that way. Want to post a patch?
Sure. I just posted another unrelated patch for amcheck this morning, so it seems a good day for it :)
—
Mark Dilger
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
Show quoted text
On Aug 26, 2021, at 4:41 PM, Mark Dilger <mark.dilger@enterprisedb.com> wrote:
Seems that way. Want to post a patch?
Sure.